Trees growover Milan.

The “Bosco Verticale” in Milan is a model for a sustainable residential building, a project for metropolitan reforestation that contributes to the regeneration of the environment and urban biodiversity without the need to expand the city’s territory.

The towers of the vertical forest, the Bosco Verticale, in Milan host almost 800 trees and thousands of perennials.

In addition to the Tree of Life that stretches its branches of wood and steel over the Italian Pavilion of Expo 2015, there is another “giant plant” that has grown in recent months in Milan: the Bosco Verticale. This “vertical forest” was built by Hines Italia and Coima. It is a part of the great residential redevelopment project in the Garibaldi-Repubblica district, a spearhead of the neo-Renaissance of Milan.

Alongside the new Porta Nuova Gardens and the Giardino De Castillia, the Bosco Verticale embodies the revolutionary idea of a skyscraper which for the first time enables its inhabitants to live in direct contact with the natural world. It is also the first example in the world of architecture that has been entirely inspired by the values of sustainability and biodiversity.

The two towers of the Bosco Verticale, which was designed by Stefano Boeri, Gianandrea Barreca and Giovanni La Varra, are 112 and 80 metres high respectively. The towers host more than 480 large and medium-height trees, 300 small trees, between 11,000 and 5,000 perennials and ground cover shrubs, all planted on 8,900 square metres of terraces. All of the plant species were carefully selected by the agronomists Laura Gatti and Emanuela Borio. In addition to green plants, there are deciduous specimens that change the colour of the towers’ “skin” with the passing of the seasons. Beeches, yellow acacias, oaks, maples, ash trees, ferns and ivy are arranged on four different façades of the two skyscrapers. They have been planted in large tanks equipped with an automatic irrigation system. Together, the plantings correspond to 20,000 square metres of forest, but they have been developed entirely on a vertical plane.

Simona Pizzi, a commercial agent, has lived on the fourteenth floor of the higher tower with her husband and her 12-year-old son since September 2014. “Our apartment is always surrounded by light,” she says. “It’s like being on a cloud with a view that embraces the Duomo, the Torre Velasca and even further away the mountains of Resegone. But the real added value comes from the green terraces, thanks to which in recent months we have directly experienced the whole cycle of the seasons. It’s like being in an enchanted forest: The blossoms of the wild apple tree have become red fruit in the autumn, hydrangeas have blossomed in the summer, camellias have flowered during winter and the red berries of the arbutus have illuminated the autumn days of fog in Milan. The maintenance of the roof gardens is taken care of by the condominium. Gardeners periodically descend on the balconies from a crane, check the irrigation system and prune any unsafe branches, without disturbing the residents. On the side of the house that does not have a balcony, we see the growing tree of the neighbours downstairs, which now houses the nest of a hawk that is hatching her eggs.”

It is no coincidence, then, that in 2014 the Bosco Verticale was awarded the prestigious International Highrise Award, which is sponsored by the Museum of Architecture in Frankfurt (Deutsches Architekturmuseum, DAM) and DekaBank. The award is presented to the most beautiful and innovative buildings over one hundred metres in height on five continents. In the most recent competition, the DAM evaluated more than 800 skyscrapers built in the previous two years. The jury decided to grant the award to the Bosco Verticale because of its symbiosis between nature and architecture. This project is the perfect model for the integration of nature and residential needs in an urban area with a high population density.

The greened terraces of the Bosco Verticale correspond to 20,000 square metres of forest.

Many vertical “green” projects have been developed in Italian cities in recent years. In Turin, for example, the OrtiAlti (ortialti.com) initiative has shown that a raised garden also promotes the rehabilitation of buildings. The project was launched in 2010 on the initiative of Studio999 with the construction of an initial roof-garden condominium in the San Salvario district. This is a format that can be exported everywhere. Its benefits include the reduction of CO2 emissions, a 75 per cent reduction of energy consumption for cooling, and almost a pound of fruit per square metre of cultivated roof area.

The Bosco Verticale, in reality, is only the first of six eco-structures that the Boeri Studio has imagined for a new “Bio Milan”. The aim is to make the city more natural, less polluted and less polluting, since the thousands of grafted plants on the buildings help to produce oxygen and absorb CO2, dust, noise, smog and heat. The “green curtain” creates a micro-climate around the apartments and reduces the temperature by 2.5 degrees Centigrade during the summer months. Bosco Verticale recently received the prestigious Gold LEED (Leadership in Energy and Environmental Design) certificate, the highest degree of energy certification and quality.

After sunset, as if by magic, the new green Milan skyscrapers are slowly lit up by a thousand flickering lights that filter through the foliage. It reminds one of the glow of fireflies that children once chased on summer evenings in the meadows on the outskirts of the city.